Methods, apparatuses and systems related to lower layer triggered mobility dual connection handover

Abstract

In an embodiment, a method implemented in a WTRU comprises receiving, from a source cell, a first message comprising information indicating a configuration including resources for measurement on RSs of the source and of a target cells; wherein resources for measurement on RSs contain a timing reference; receiving RSs from the source and from the target cells; performing a time difference measurement between source cell RSs and target cell RSs; on condition that the measured time difference is within a threshold amount from zero: transmitting, to the source cell, a second message comprising information indicating the measured time difference between the source and the target cell RSs; receiving, from the source cell, a third message comprising information indicating downlink scheduling resources on the target cell; and receiving, from the target cell, a fourth message comprising information indicating release of configuration associated with the source cell.

1 . A method implemented in a wireless transmit/receive unit (WTRU) comprising:
 receiving, from a source cell, a first message comprising information indicating a handover configuration including resources for measurement on reference signals (RSs) of the source cell and of a target cell; wherein resources for measurement on RSs contain a timing reference;   receiving RSs from the source cell and from the target cell;   performing at least one time difference measurement between source cell RSs and target cell RSs;   on condition that the at least one measured time difference is within a threshold amount from zero:
 transmitting, to the source cell, a second message comprising information indicating the measured time difference between the source cell RSs and the target cell RSs; 
 receiving, from the source cell, a third message comprising information indicating downlink scheduling resources on the target cell; and 
 receiving, from the target cell, a fourth message comprising information indicating release of configuration associated with the source cell. 
   
     
     
         2 . The method of  claim 1  comprising:
 performing at least one radio quality measurement on at least one target cell RS; 
 wherein transmitting, to the source cell, the second message is on condition that the radio quality measurement satisfies a radio quality condition threshold. 
 
     
     
         3 . The method of  claim 2 , wherein the second message further comprises information indicating result of the at least one radio quality measurement. 
     
     
         4 . The method of  claim 1  comprising
 on condition that the at least one measured time difference is above a threshold amount from zero: 
 transmitting, to the source cell, a fifth message comprising information indicating the measured time difference between the source cell RSs and the target cell RSs; and 
 re-performing at least one time difference measurement between source cell RSs and target cell RSs. 
 
     
     
         5 . The method of  claim 1  comprising
 on condition that the at least one measured time difference is within the threshold amount from zero: 
 performing channel state information CSI acquisition for the target cell resources according to the measured time difference. 
 
     
     
         6 . The method of  claim 1  comprising
 on condition that the at least one measured time difference is within the threshold amount from zero: 
 performing, beam refinement, for the target cell resources according to the measured time difference. 
 
     
     
         7 . The method of  claim 1 , wherein the handover configuration includes a subset of downlink measurement RS on the target for which to use for determining downlink reception time difference between source and target RSs, and/or wherein the handover configuration includes a subset of downlink measurement RS on the source for which to use for determining downlink reception time difference between source and target RSs. 
     
     
         8 . The method of  claim 1 , wherein the fourth message is an indication on physical downlink control channel (PDCCH) from the target cell to release configuration associated with the source cell. 
     
     
         9 . The method of  claim 7 , comprising receiving an indication on PDCCH from the source cell to start monitoring the PDCCH on the target cell. 
     
     
         10 . The method of  claim 1 , wherein the second message is a CSI or MAC CE. 
     
     
         11 . A wireless transmit/receive unit (WTRU) comprising a processor, a transmitter, a receiver and a memory, configured to:
 receive, from a source cell, a first message comprising information indicating a handover configuration including resources for measurement on reference signals (RSs) of the source cell and of a target cell; wherein resources for measurement on RSs contain a timing reference;   receive RSs from the source cell and from the target cell;   perform at least one time difference measurement between source cell RSs and target cell RSs;   on condition that the at least one measured time difference is within a threshold amount from zero:
 transmit, to the source cell, a second message comprising information indicating the measured time difference between the source cell RSs and the target cell RSs; 
 receive, from the source cell, a third message comprising information indicating downlink scheduling resources on the target cell; and 
 receive, from the target cell, a fourth message comprising information indicating release of configuration associated with the source cell. 
   
     
     
         12 . The WTRU of  claim 11  configured to:
 perform at least one radio quality measurement on at least one target cell RS; 
 on condition that the radio quality measurement satisfies a radio quality condition threshold, transmit, to the source cell, the second message. 
 
     
     
         13 . The WTRU of  claim 12 , wherein the second message further comprises information indicating result of the at least one radio quality measurement. 
     
     
         14 . The WTRU of  claim 11  configured to:
 on condition that the at least one measured time difference is above a threshold amount from zero: 
 transmit, to the source cell, a fifth message comprising information indicating the measured time difference between the source cell RSs and the target cell RSs; and 
 re-perform at least one time difference measurement between source cell RSs and target cell RSs. 
 
     
     
         15 . The WTRU of  claim 11  configured to:
 on condition that the at least one measured time difference is within the threshold amount from zero: 
 perform channel state information CSI acquisition for the target cell resources according to the measured time difference. 
 
     
     
         16 . The WTRU of  claim 11  configured to:
 on condition that the at least one measured time difference is within the threshold amount from zero: 
 perform, beam refinement, for the target cell resources according to the measured time difference. 
 
     
     
         17 . The WTRU of  claim 11 , wherein the handover configuration includes a subset of downlink measurement RS on the target for which to use for determining downlink reception time difference between source and target RSs, and/or wherein the handover configuration includes a subset of downlink measurement RS on the source for which to use for determining downlink reception time difference between source and target RSs. 
     
     
         18 . The WTRU of  claim 11 , wherein the fourth message is an indication on physical downlink control channel (PDCCH) from the target cell to release configuration associated with the source cell. 
     
     
         19 . The WTRU of  claim 18 , configured to receive an indication on PDCCH from the source cell to start monitoring the PDCCH on the target cell. 
     
     
         20 . The WTRU of  claim 11 , wherein the second message is a CSI or MAC CE.